The phenomenon of two-beam coupling (TBC), which is also known as two-wave mixing (TWM), may provide a discriminator for separating coherent from incoherent light, thus maintaining fidelity in the phase information. As such, two-beam coupling is a coherent light discriminator and may therefore be used for applications such as beam combining, image amplification, and digital holography.
Although coherent amplification may have almost unlimited applications in the field of photonics, in most prior art systems, only photorefractive materials have been used for this purpose. Photorefractive materials may generally initiate two-beam coupling by mechanisms involving charge diffusion, the application of external electric fields (e.g., direct current (DC) electric fields), and have a large-scale order (e.g., crystallinity). Each of these features introduce certain limitations on the applicability of this technique. As such, there remains a need for improved devices, systems, and methods for coherent amplification, e.g., without using photorefractive materials.